Metal fossa-eminence prostheses (hemijoint replacements) are generally known and commercially available. These devices are materials that are rigidly fixed to the articular fossa and/or materials that resurface the articular fossa to reverse bone-on-bone contact in patients with osteoarthritis or fibrous/osseous ankylosis. There remains a continuing need to improve fossa-eminence type prostheses. Prostheses that enhance joint motion are desirable. Improved instruments for use with eminence fossa implant surgical procedures involving fossa-eminence prostheses would also be desirable.